In recent years, streaming services that allow users to download rich content such as music from content servers to information terminals have begun to prevail. In the information terminal that utilizes such services, the downloaded content is temporarily stored in memory, and the stored content is read out from memory and played back in accordance with a user request.
On the other hand, it is proposed to use a hard disk (HDD) as a memory used to store contents. If the HDD is used as the memory, a large amount of content can be stored with lower cost than with use of a flash memory or the like. However, the HDD is generally vulnerable to shock and easily breaks.
Hence, content stored in the HDD is backed up to an external storage device. Desirably, one can restore backup files of the content from the external storage device to the HDD when the content cannot be used due to a problem with the HDD or the like.
For example, in a known method, when the content server downloads content with the use condition to the information terminal, it appends the network address of a backup server to the content to be downloaded. The information terminal transmits the content to the backup server by using the network address upon backing the downloaded content. The backup server saves the transmitted content in correspondence with the telephone number of the information terminal as the transmission source. However, this method requires a dedicated backup server, and imposes the content provider an economical burden. Note that the technique that uses the backup server is disclosed in detail in Jpn. Pat. Appln. KOKAI Publication 2004-48180.
On the other hand, a technique for backing up content stored in a mobile telephone or mobile terminal such as a PDA or the like using a personal computer has been proposed. For example, content stored in a HDD of a mobile terminal is encrypted together with its usage rule, and the encrypted content including the usage rule is copied to the personal computer intact. When the content is deleted due to a problem with the HDD or the like, the encrypted content including the usage rule is restored from the personal computer to the HDD.
Also, in order to use a memory of a mobile terminal effectively, a user can move the downloaded content and the usage rule to a personal computer and delete the downloaded content and usage the rule from the memory after backing up.
Here, it is required to play the content, which is copied from the mobile terminal as a backup file, in the personal computer having a large display.
However, it is prohibited to play the content other than the terminal which downloaded the content.